Abstract. Local and global bifurcation structure of the forced Lorenz model in the r-F plane is investigated. The forced Lorenz model is a conceptual model for understanding the influence of the slowly varying boundary forcing like Sea Surface Temperature (SST) on the Indian summer monsoon rainfall variability. Shift in the probability density function between the two branches of the Lorenz attractor as a function of SST forcing is calculated. It is found that the one-dimensional return map (cusp map) splits into two cusps on introduction of forcing.